1. Field of the Invention
The present invention relates to a new process for the production of chemically resistant coatings using a coating agent based on organic polyisocyanates, organic compounds having alcoholic hydroxyl groups and water, the coating agent additionally containing combinations of glycerine and hydroxides or oxides of alkaline earth metals to prolong the processing time and improve the chemical resistance thereof.
2. Description of the Prior Art
The use of hydroxides or oxides of alkaline earth metals in the production of unfoamed polyurethane plastics using water-containing reactive systems based on organic polyisocyanates and organic compounds having isocyanate-reactive groups is already known. DE-PS No. 1,170,627, for example, describes the effect of calcium oxide as a dehydrating agent in polyurethane systems. GB-PS 1,147,695 describes, among other things, the use of calcium hydroxide in water-containing reactive systems of this type in the production of unfoamed polyurethane plastics. Furthermore, hydraulic cements were used to prevent foaming in water-containing polyurethane systems (c.f., by way of example, DE-OS Nos. 2,113,046, 2,254,251, 2,113,042, 2,300,206 or DE-AS Nos. 1,924,468). Whereas the mechanical properties and the chemical resistance of the coatings produced according to these prior publications were completely satisfactory, the problem of a sufficient processing time has hitherto not been satisfactorily solved.
Coating compositions of this type have to have a processing time of at least 30 minutes to facilitate expert processing.
Thus an object of the present invention was to improve the known processes for the production of chemically resistant plastics, more particularly surface coatings based on water and inorganic filler-containing polyurethane systems, such that the coating agents which are used have a sufficient processing time and enable coatings to be produced which are at least equal to corresponding systems of prior art from the point of view of the chemical resistance and other properties thereof.
This object is achieved by the present process which is described in more detail in the following.